Suppression of hepatoma tumor growth by systemic administration of the phytotoxin gelonin driven by the survivin promoter

Abstract

Hepatocellular carcinoma (HCC) is one of the most common types of cancer worldwide. However, there is currently no effective therapy strategy in the clinical practice. Recombinant phytotoxin gelonin fused to other factors have been used to treat different cancers. But there have been no reports of gelonin gene therapy. In this study, we have constructed a recombinant plasmid which contained a tumor-specific survivin promoter to drive phytotoxin gelonin (pSur-Gel). And the cytotoxicity effects of pSur-Gel in HCC were also validated both in vitro and in vivo. The expression level of survivin was detected in different liver cancer cell lines and normal liver cell lines by western blot analysis, and a survivin promoter-driven green fluorescent protein (GFP) expression vectors (pSur-GFP) was also tested in liver cancer cell line HepG2 and normal liver cell line LO2. Moreover, phytotoxin gelonin expression experiment and cytotoxicity experiment of pSur-Gel was performed in HepG2 cells and LO2 cells in vitro. Furthermore, anti-tumor effect of pSur-Gel against HepG2 xenografts and toxicity of this gene were evaluated in the mice model. Finally, LDH release assay, apoptosis assay and immunoblot analyse LC3 conversion (LC3-I to LC3-II) were tested. We found that the expression of survivin protein was higher in liver cancer cell lines compared with the normal liver cells. Further study showed that the pSur-GFP and pSur-Gel was expressed specially in liver cancer cell other than in normal liver cells. pSur-Gel plasmid could effectively inhibit the proliferation of liver cancer cells (*P<0.05), and significantly repress the growth of HepG2 xenografts via intravenous in vivo (*P<0.05). Otherwise, compared to cytomegalovirus promoter-driven gelonin expression vectors (pCMV-Gel), no significantly systemic toxicity or organ injuries had been observed in pSur-Gel treated mice. Further studies revealed that the phytotoxin gelonin induced cell death might be mediated by apoptosis and the damage of cell membrane. Taken together, treating hepatocellular carcinoma with the pSur-Gel may be a novel and interesting cancer gene therapy protocol and is worthy of further development for future clinical trials. liver cancer, gelonin, survivin promoter, gene therapy.